1. Field of the Invention
The present invention relates to a graphic display processing method for displaying a graphic image through a hidden processing for eliminating hidden lines from perspective represents of a three-dimensional structure, by use of a painting function of a graphic terminal device.
2. Description of the Related Art
Conventional methods of displaying a three-dimensional structure, such as three-space objects, a curved surface or an impurity concentration distribution in a predetermined cross section of a semiconductor, by means of line drawing, include a floating horizontal line algorithm and cross-hatching algorithm (e.g. see "JISSEN COMPUTER GRAPHICS", edited by Fujio YAMAGUCHI, Nikkan Kogyo Shinbun-Sha).
According to the floating horizontal line algorithm, an image is described by first drawing a line closest to a view point, and a hidden-line processing is performed on an overlapped portion of a front image and a rear image. Specifically, an overlapped portion of the rear image is represented by a hidden line. In the hidden-line processing, intersections of the front and rear images are found by calculations. On the basis of the found intersections, the hidden-line processing is carried out. Thus, a great amount of calculations are required and high-speed hidden-line processing cannot be performed.
On the other hand, according to the cross-hatching algorithm, a plurality of two-dimensional images are sequentially described in an overlapped manner from the image farthest from a viewpoint to the image closest thereto. By painting the overlapped portion of the front image, the hidden-line processing of the rear image is effected. According to this painting method, the hidden-line processing is carried out without performing a great amount of calculations, unlike the floating horizontal line algorithm. There are such problems in floating horizontal line algorithm that in a line segment which is to be or not to be displayed, the visible/invisible determination for intersections are performed for one intersection; thus, if the visible/invisible state varies with respect to plural intersections within one region, the hidden-line processing cannot be carried out exactly.